Powered dispensing tool

ABSTRACT

A powered dispensing tool includes a housing, a motor positioned within the housing, a rack coupled to the motor for powered translation in at least one of a forward direction and a reverse direction, and a transmission selectively coupling the motor and the rack. The transmission includes an input ring rotatable in response to rotation of the motor in a first direction corresponding with powered translation of the rack in the forward direction, a first clutch member engaged with the rack through an intermediate gear, and a second clutch member that receives torque from the input ring and that is movable in response to rotation of the motor in the first direction toward a first position engaging the first clutch member. The second clutch member is also movable in response to rotation of the motor in an opposite, second direction toward a second position disengaged from the first clutch member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to co-pending U.S. Provisional PatentApplication Nos. 61/413,734 filed on Nov. 15, 2010 and 61/524,655 filedon Aug. 17, 2011, the entire contents of both of which is incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention relates to power tools, and more particularly topowered dispensing tools

BACKGROUND OF THE INVENTION

Dispensing tools, such as those used for dispensing caulk, adhesives, orlike materials, are typically manually operated by squeezing or graspinga handle of the dispensing tool. The handle is typically connected to arack via an advancing mechanism (e.g., a ratchet and pawl-typemechanism) to incrementally advance the rack and cause the caulk,adhesive, or like material to be discharged from a cartridge. Suchmanually operated dispensing tools can be difficult to control andstrenuous, thereby fatiguing the user and possibly shortening theduration of time the manually operated dispensing tool may be usedbefore the user requires rest.

SUMMARY OF THE INVENTION

The invention provides, in one aspect, a powered dispensing toolincluding a housing, a motor at least partially positioned within thehousing, a rack operably coupled to the motor for powered translation inat least one of a forward direction and a reverse direction, and atransmission selectively operably coupling the motor and the rack. Thetransmission includes an input ring rotatable in response to rotation ofthe motor in a first direction corresponding with powered translation ofthe rack in the forward direction, a first clutch member engaged withthe rack through at least one intermediate gear, and a second clutchmember that receives torque from the input ring and that is movable inresponse to rotation of the motor in the first direction toward a firstposition engaging the first clutch member. The second clutch member isalso movable in response to rotation of the motor in an opposite, seconddirection toward a second position disengaged from the first clutchmember.

Other features and aspects of the invention will become apparent byconsideration of the following detailed description and accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective view of a powered dispensing toolaccording to an embodiment of the invention.

FIG. 2 is a rear perspective view of the powered dispensing tool of FIG.1.

FIG. 3 is an exploded, front perspective view of the powered dispensingtool of FIG. 1.

FIG. 4 is an exploded, front perspective view of a transmission in thepowered dispensing tool of FIG. 1.

FIG. 5 is an exploded, rear perspective view of the transmission of FIG.4.

FIG. 6 is a cutaway view of the powered dispensing tool of FIG. 1,illustrating the orientation of an input ring and a drive shaft of thetransmission when a motor of the dispensing tool is deactivated.

FIG. 7 is a partial cross-sectional view of the powered dispensing toolof FIG. 1 along line 7-7 in FIG. 6, illustrating a clutch of thetransmission in a disengaged configuration corresponding with theorientation of the input ring and drive shaft shown in FIG. 6.

FIG. 8 is a cutaway view of the powered dispensing tool of FIG. 1,illustrating the orientation of the input ring and the drive shaft afterthe motor is activated.

FIG. 9 is a partial cross-sectional view of the powered dispensing toolof FIG. 1 along line 9-9 in FIG. 8, illustrating the clutch in anengaged configuration corresponding with the orientation of the inputring and drive shaft shown in FIG. 8.

FIG. 10 is a front perspective view of the powered dispensing tool ofFIG. 1, illustrating various combinations of cartridge housings andplungers that may be used with the tool.

FIG. 11 is an enlarged, cross-sectional view of one of the plungersshown in FIG. 10 attached to the rack.

FIG. 12 is a schematic illustrating various electronic components of thepowered dispensing tool of FIG. 1.

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways. Also, it is to be understood thatthe phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting.

DETAILED DESCRIPTION

A powered dispensing tool 10 according to an embodiment of the inventionis shown in FIGS. 1 and 2. The tool 10 includes a main housing 14 and acartridge housing 18 attached to the main housing 14 for supporting atubular cartridge of caulk, adhesive, or other material to be dispensed.The tool 10 also includes a rack 22 having a first end 26 coupled to aplunger 30 and a second end 34 accessible from the rear of the mainhousing 14. A handle 36 is coupled to the second end 34 of the rack 22to facilitate grasping the rack 22 to manually advance or retract therack 22 relative to the main housing 14. As will be described in greaterdetail below, the plunger 30 is movable within the cartridge housing 18in response to the rack 22 being driven or otherwise moved in a forwardor reverse direction.

With reference to FIG. 3, the tool 10 includes a power train assembly 38positioned within the main housing 14. The power train assembly 38includes an electric motor 42, a three-stage planetary transmission 46,and a transmission 50 for converting the rotational output of theplanetary transmission 46 to a translational output of the rack 22. Inthe illustrated construction of the tool 10, the motor 42 is configuredas a DC motor that receives power from an on-board power source (e.g., abattery 54). The battery 54 may include any of a number of differentnominal voltages (e.g., 12V, 18V, etc.), and may be configured havingany of a number of different chemistries (e.g., lithium-ion,nickel-cadmium, etc.). Alternatively, the motor 42 may be powered by aremote power source (e.g., a household electrical outlet) through apower cord. The motor 42 is selectively activated by depressing atrigger 58 which, in turn, actuates a switch 62. The switch 62 may beelectrically connected to the motor 42 via a top-level or mastercontroller or one or more circuits as described below and shown in FIG.12.

With reference to FIGS. 4 and 5, the transmission 50 includes atransmission housing 66 and a pinion 70 supported for rotation in thetransmission housing 66 by two roller bearings 74. The pinion 70 iscoupled to an output carrier 78 of the planetary transmission 46 (FIG.3) to receive torque therefrom. With reference to FIG. 4, thetransmission 50 also includes a drive shaft 82 having opposed ends 86,90 supported for rotation in the transmission housing 66 by respectivebearings 94, 98, and an input ring 102 engaged with the pinion 70 andpositioned coaxial with the drive shaft 82. The input ring 102 includesa hub 106 having a cylindrical outer periphery received within the innerrace of the bearing 94 to journal the input ring 102 relative to thetransmission housing 66. A drive portion 110 of the drive shaft 82includes parallel flats 114, and the hub 106 of the input ring 102includes opposed, convex lugs 118 that are engageable with therespective flats 114. As a result of this arrangement, the input ring102 may be rotated by the pinion 70 relative to the drive shaft 82 aparticular amount (e.g., 40 degrees) before the lugs 118 come intoengagement with the respective flats 114, after which time the driveshaft 82 and the input ring 102 will co-rotate.

With reference to FIGS. 4 and 5, the transmission 50 also includes anoutput gear 122 engaged with the rack 22 and supported for rotation inthe transmission housing 66 with bushings 126, and a speed-reducing geartrain 130 coupled to the output gear 122. In the illustratedconstruction of the tool 10, the gear train 130 includes a first gear134 having a cylindrical aperture 138 through which a cylindricalportion 142 of the drive shaft 82 is inserted. As such, the first gear134 is journaled for rotation relative to the cylindrical portion 142 ofthe drive shaft 82. The gear train 130 also includes a second gear 146having a non-circular aperture 150 in which a portion of the output gear122 having a corresponding non-circular cross-sectional shape isreceived. As such, the output gear 122 and the second gear 146 of thegear train 130 are coupled for co-rotation. An interference or press-fitmay be utilized to secure the output gear 122 to the second gear 146.Alternatively, any of a number of different mechanical fasteners may beutilized to secure the output gear 122 to the second gear 146, or as afurther alternative, the output gear 122 may be integrally formed withthe second gear 146 as a single piece.

With continued reference to FIGS. 4 and 5, the transmission 50 furtherincludes a clutch 154 that is engaged in response to rotation of themotor 42 in a first direction corresponding with powered translation ofthe rack 22 in a forward or advancing direction to dispense materialfrom a cartridge supported in the cartridge housing 18. The clutch 154includes a clutch or an input member 158 having a plurality of axiallyextending teeth 162 and a slide member 166 positioned between the inputmember 158 and the input ring 102. The slide member 166 includes a hub170 having an aperture 174 with a cross-sectional shape corresponding tothat of the drive portion 110 of the drive shaft 82. Accordingly, theslide member 166 is axially slidable on the drive portion 110 and fixedfor co-rotation with the drive shaft 82. The input member 158 includesan aperture 178 with a cross-sectional shape corresponding with theouter periphery of the hub 170 on the slide member 166. The hub 170 isreceived within the aperture 178 in a manner permitting relative axialmovement between the slide member 166 and the input member 158, andfixing the input member 158 for co-rotation with the slide member 166.As such, both the input member 158 and the slide member 166 co-rotatewith the drive shaft 82 at all times.

With reference to FIG. 5, the input ring 102 includes three ramps 182(only one of which is visible) extending toward the slide member 166that are selectively engageable with three corresponding ramps 186 onthe slide member 166 (FIG. 4) in response to relative rotation betweenthe input ring 102 and the slide member 166. The slide member 166 istherefore movable along the drive shaft 82 between a retracted position,in which the ramps 182, 186 are misaligned (i.e., not engaged), and anextended position, in which the ramps 182, 186 are aligned (i.e.,engaged).

With reference to FIGS. 4 and 5, the clutch 154 also includes a clutchor an output member 190 coupled for co-rotation with the first gear 134of the speed-reducing gear train 130. In the illustrated construction ofthe tool 10, the output member 190 is integrally formed with the firstgear 134 as a single piece. Alternatively, any of a number of differentmechanical connections may be utilized to couple the output member 190and the first gear 134 (e.g., a press-fit, welding, a key and keywayarrangement, adhesives, fasteners, etc.). The output member 190 shares ahub with the first gear 134, and further includes a circular rim havinga plurality of axially extending teeth 194 in facing relationship withthe teeth 162 on the input member 158. Sufficient clearance existsbetween the cylindrical portion 142 of the drive shaft 82 and the outputmember 190 such that the output member 190 is rotatable, with the firstgear 134, relative to the drive shaft 82. Each of the teeth 162, 194 onthe respective input and output members 158, 190 includes a drivesurface 198 on one side that is oriented generally parallel to arotational axis 202 of the drive shaft 82, and a ramp surface 206 on theother side that is generally inclined relative to the rotational axis202. When the input member 158 rotates in a counter-clockwise directionfrom the frame of reference of FIG. 4 to engage the respective drivesurfaces 198 of the teeth 194, torque is transferred from the inputmember 158 to the output member 190. The ramp surfaces 206 of therespective teeth 162, 194 are not intended to be used during the normalcourse of operation of the tool 10, but rather are provided as a measureto prevent torque transfer between the input and output members 158, 190should the output member 190 overrun the input member 158 (e.g., whenthe rack 22 is manually advanced by the operator of the tool 10).

With reference to FIGS. 4 and 5, the clutch 154 also includes a returnspring 210 positioned between the input member 158 and the output member190 to bias the input member 158 toward the input ring 102, and a delayspring 214 positioned between the slide member 166 and the input member158. When the slide member 166 is in the extended position, the delayspring 214 biases the input member 158 toward a corresponding extendedposition to engage the output member 190. However, when the slide member166 is in the retracted position, the input member 158 is returned to acorresponding retracted position by the return spring 210 such thatsufficient spacing exists between the input member 158 and the outputmember 190 to prevent engagement of the respective teeth 162, 194 on theinput and output members 158, 190.

With reference to FIG. 10, the powered dispensing tool 10 includes aquick-change assembly 218 for adapting different style and sizecartridge housings 18 to the main housing 14 of the tool 10 such thatthe tool 10 may be used with cardboard tube-style cartridges 18 a, 18 bor sausage pack cartridges 18 c, 18 d of different sizes. In theillustrated construction of the tool 10, the quick-change assembly 218is configured as a collar 222 with internal threads 226 that is axiallysecured to the main housing 14 of the tool 10. The collar 222, however,is free to rotate relative to the housing 14. The cartridge housings 18a, 18 b are adapted to receive cardboard tube-style cartridges, and thecartridge housings 18 c, 18 d are adapted to receive sausage packcartridges. Each of the housings 18 includes a universal connectorhaving external threads 230 that correspond with the internal threads226 on the collar 222, such that any of the housings 18 may be securedto the main housing 14. No additional structure is utilized to interlockthe housings 18 to the collar 222 to inhibit inadvertent removal of anyof the housings 18 from the collar 222 and the main housing 14.

Likewise, the plunger 30 may be replaced with other plungers havingdifferent sizes or configurations than the plunger 30. The plunger 30illustrated in FIGS. 1 and 2 is configured for use with cardboardtube-style cartridges and either of the cartridge housings 18 a, 18 bshown in FIG. 10. Another plunger 234 is used in conjunction with theeither of the cartridge housings 18 c, 18 d when dispensing materialfrom a sausage pack. As shown in FIGS. 10 and 11, the plunger 234includes a central, tapered dome 238 and a circular seal lip 242extending from the dome 238. The dome 238 includes a cylindrical bore246 facing the rear end of the plunger in which the rack 22 is received(FIG. 11). A fastener (e.g., a screw 250) is received within a recess254 facing the forward end of the plunger 234 to secure the plunger 234to the rack 22. The lip 242 includes a single, radially extending slot256 (FIGS. 10 and 11) through which air may vent from one side of theplunger 234 to the other side of the plunger 234 when the plunger 234 issituated in one of the sausage pack-style cartridge housings 18 c, 18 dshown in FIG. 10.

With reference to FIG. 12, the tool 10 further includes a stroke-limitcircuit 258 in electrical communication with the motor 42, a Hall-effectsensor 262 in electrical communication with the stroke-limit circuit258, and a magnet 266 coupled to the rack 22 at a location proximate theend 34 of the rack 22 opposite the plunger 30. Although not shown, thestroke-limit circuit 258 may be a component, or incorporated as asoftware program, in a top-level or master controller in the tool 10.Though schematically illustrated in FIG. 12, the magnet 266 may becoupled to the rack 22 in any of a number of different manners (e.g.,using a press-fit, adhesives, fasteners, etc.). The magnet 266 may alsobe at least partially positioned within the rack 22 such that little tonone of the magnet 266 is visible from the outer periphery of the rack22.

Upon detection of the magnetic field emanated by the magnet 266, theHall-effect sensor 262 is actuated which, in turn, provides a signal tothe stroke-limit circuit 258 to deactivate the motor 42. In this manner,the end 34 of the rack 22 opposite the plunger 30 is prevented fromimpacting the main housing 14 during advancement of the rack 22 ormovement of the rack 22 in a forward, material-dispensing direction,thereby defining a predetermined stroke limit to the rack 22 and plunger30.

With continued reference to FIG. 12, the tool 10 also includes acurrent-monitoring circuit 270 in electrical communication with themotor 42. Although not shown, the current-monitoring circuit 270 may bea component, or incorporated as a software program, in a top-level ormaster controller in the tool 10. Alternatively, the current-monitoringcircuit 270 may be a separate and stand-alone circuit defined byhardware and not associated with any controllers in the tool 10.

The rack 22 undergoes a relatively slow linear motion for dispensingcaulk, adhesives, or other materials from cartridges. This slow lineardispensing speed is produced by reducing the motor speed through theplanetary transmission 46 and the speed-reducing gear train 130,followed by the output gear 122 driving the rack 22. In normaloperation, the force developed by the rack 22 is within an acceptablerange that will not affect the reliability of the tool 10. However, ifthe rack 22 encounters an obstacle that causes the motor speed to slowdramatically or stall completely, the amount of force developed by therack 22 will increase substantially over a short period of time. Such anincreased force may be large enough to damage to the planetarytransmission 46, the rack 22, or the cartridge housing 18. Thecurrent-monitoring circuit monitors 270 this force and quickly takescorrective action should the force become too high.

The force developed by the rack 22 is proportional to the torquedeveloped by the motor 42 which, in turn, is proportional to the motorcurrent. Therefore, monitoring motor current provides a very goodindication of the force exerted on the rack 22. If a motor currentfeedback signal rises at a rate higher than a predetermined value, thecurrent-monitoring circuit 270 will cease to drive the motor 42 and therack 22 in the forward, material-dispensing direction, and will insteaddrive the motor 42 and the rack 22 in a reverse direction for a shortinterval before deactivating the motor 42. This condition may occur, forexample, if a blockage is encountered within the cartridge which, inturn, prevents material from being discharged from the cartridge. Aprocess for monitoring motor current, which can be implemented in thecurrent-monitoring circuit 270 of FIG. 12, is shown and described ingreater detail in published U.S. Patent Application No. 2010/0001017(the “'017 Publication”), the entire contents of which is herebyincorporated by reference.

With continued reference to FIG. 12, the tool 10 further includes amotor-control circuit 274 in electrical communication with the motor 42.Although not shown, the motor-control circuit 274 may be a component, orincorporated as a software program, in a top-level or master controllerin the tool 10. Alternatively, the motor-control circuit 274 may be aseparate and stand-alone circuit defined by hardware and not associatedwith any controllers in the tool 10.

When the trigger 58 is depressed, the motor-control circuit 274activates the motor 42. However, rather than immediately driving themotor 42 at a predetermined speed, or at a user-selected speed inaccordance with the adjustment of a potentiometer 278 (FIG. 12) incommunication with the motor-control circuit 274, a soft-start featureof the dispensing tool 10 allows the rack 22, moving in the forward ormaterial-dispensing direction, to be accelerated from rest to thepredetermined or user-selected speed over a short period of time (i.e.,typically less than one second). The motor-control circuit 274 graduallyincreases the voltage applied to the motor 42, and in doing so reducesthe peak current drawn by the motor 42 during startup. The motor-controlcircuit 274 also reduces the peak torque delivered by the motor 42during startup, and therefore provides smoother dispensing of materialduring startup. Further, incorporating the soft-start feature in themotor-control circuit 274 increases the life expectancy and reduces wearof the tool 10. A process for providing the soft-start feature, whichcan be implemented in the motor-control circuit 274 of FIG. 12, is shownand described in greater detail in the '017 Publication.

With continued reference to FIG. 12, the tool 10 also includes anauto-reverse circuit 282 in electrical communication with the motor 42.Although not shown, the auto-reverse circuit 282 may be a component, orincorporated as a software program, in a top-level or master controllerin the tool 10. Alternatively, the auto-reverse circuit 282 may be aseparate and stand-alone circuit defined by hardware and not associatedwith any controllers in the tool 10.

It is desirable to minimize or eliminate dispensing material fromexcreting from the tool 10 after operation has ceased. This can beachieved by providing a control scheme for momentarily reversing therotational direction of the motor 42 after the user has released thetrigger 58. After dispensing is halted, the material within thecartridge is allowed to expand within the cartridge to alleviate theresidual pressure within the cartridge from the dispensing operation. Asis described in greater detail below, momentary reversal of the motor 42by the auto-reverse circuit 282 causes the clutch 154 to disengage,thereby disconnecting the rack 22 from the motor 42. The plunger 30 andthe rack 22 may therefore be pushed rearward by the expanding materialwithin the cartridge without concern of back-driving the motor 42.

When the trigger 58 is actuated again to reactivate the motor 42, theclutch 154 is still disengaged. Initial movement of the motor 42 acts toreengage the clutch 154 as described above before the plunger 30 startsmoving toward the tubular cartridge within the cartridge housing 18. Insome embodiments, the motor 42 may run for about 0.6 seconds at itshighest speed setting to reengage the clutch 154 before the plunger 30starts moving. In contrast, the motor 42 may run for about 6 seconds atits lowest speed setting to reengage the clutch before the plunger 30starts moving. In order to minimize this relatively long delay inreengaging the clutch 154, a pre-drive circuit may be incorporated withthe motor control circuit 274 for operating the motor 42 at full speed(i.e., at the highest speed setting) for a brief interval when thetrigger 58 is actuated, regardless of the operating speed set by thepotentiometer 278. The brief interval is slightly less than the amountof time required to reengage the clutch 154 if the motor 42 was run atits highest speed setting. For example, the pre-drive circuit may drivethe motor 42 at full speed for about 0.5 seconds if it normally takesthe motor 42 about 0.6 seconds to reengage the clutch 154 at the highestspeed setting. After the brief interval, the pre-drive circuit revertsthe operating speed of the motor 42 to whatever speed the user has setwith the potentiometer 278 and the position of the trigger 58. Thepre-drive circuit thereby reduces the delay associated with reengagingthe clutch 154 prior to material dispensing, while still maintaining theuse of the clutch 154 between the motor 42 and the rack 22 to avoidmaterial droop.

In some embodiments, the tool 10 may include a sensor that detects orsenses when the clutch 154 is engaged. In such embodiments, thepre-drive circuit may continuously drive the motor 42 at full speeduntil the sensor detects that the clutch 154 is reengaged.

In operation of the tool 10, the input ring 102 is initially orientedrelative to the drive shaft 82 such that the lugs 118 are spaced fromthe respective flats 114 on the drive shaft 82 (FIG. 6), and the outputmember 190 is in its retracted position (FIG. 7). As such, the outputmember 190, the speed-reducing gear train 130, and the output gear 122may be rotated relative to the drive shaft 82 in response to theoperator grasping the end 34 of the rack 22 opposite the plunger 30 andpulling the rack 22 rearward to create sufficient spacing in thecartridge housing for insertion of a tubular cartridge or a sausage packcontaining caulk, adhesive, or other material to be dispensed. After thetubular cartridge or sausage pack is loaded, the rack 22 may be pushedforward to initially engage the plunger 30 with the rear of the tubularcartridge or sausage pack, causing the output member 190, thespeed-reducing gear train 130, and the output gear 122 to rotaterelative to the stationary drive shaft 82.

When the user depresses the trigger 58, the motor 42 is activated todrive the planetary transmission 46, the pinion 70, and the input ring102. As discussed above, the motor-control circuit 274 may implement thesoft-start feature to slowly accelerate the motor 42 to a desiredoperating speed. The input ring 102 will continue to rotate relative tothe stationary drive shaft 82 until the lugs 118 engage the respectiveflats 114 on the drive shaft 82 (i.e., after about 40 degrees ofrelative rotation; see FIG. 8). During this time, the ramps 186, 182 onthe slide member 166 and the input ring 102 are rotated into alignmentand engage, thereby axially displacing the slide member 166 from itsretracted position (FIG. 7) to its extended position (FIG. 9). If theteeth 162 of the input member 158 are aligned with the respective teeth194 on the output member 190, the delay spring 214 is compressed.Rotation of the drive shaft 82, the slide member 166, and the inputmember 158 continues until the teeth 162 of the input member 158 aremisaligned with the respective teeth 194 on the output member 190, atwhich time the delay spring 214 rebounds to cause the input member 158to engage the output member 190.

Subsequent engagement of the drive surfaces 198 on the respective teeth162, 194 of the input and output members 158, 190 rotationallyinterlocks the input member 158 and the output member 190. Torque fromthe drive shaft 82 is then transferred through the input member 158,through the output member 190, and to the speed-reducing gear train 130,which rotates the output gear 122 and drives the rack 22 in a forwarddirection to dispense caulk, adhesive, or other material from thetubular cartridge or sausage pack.

When the user releases the trigger 58, the auto-reverse circuit 282momentarily drives the motor 42 in a reverse direction to rotate theinput ring 102 relative to the drive shaft 82 in a reverse direction,thereby disengaging the lugs 118 from the respective flats 114 on thedrive shaft 82. During this time, the ramps 186, 182 on the slide member166 and the input ring 102 are misaligned and disengaged, permitting thereturn spring 210 to bias the input member 158 and slide member 166toward their respective retracted positions, thereby disengaging theinput member 158 from the output member 190. The output member 190,therefore, is again permitted to rotate relative to the drive shaft 82in response to retraction of the rack 22 caused by expansion of thecaulk, adhesive, or other material to be dispensed within the cartridgesupported within the cartridge housing 18. Should the user of the tool10 desire to change material cartridges, the user may grasp the end 34of the rack 22 and pull to manually retract the rack 22 to change thecartridge.

Although the invention has been described in detail with reference tocertain preferred embodiments, variations and modifications exist withinthe scope and spirit of one or more independent aspects of the inventionas described.

What is claimed is:
 1. A powered dispensing tool comprising: a housing;a motor at least partially positioned within the housing; a rackoperably coupled to the motor for powered translation in at least one ofa forward direction and a reverse direction; and a transmissionselectively operably coupling the motor and the rack, the transmissionincluding an input ring rotatable in response to rotation of the motorin a first direction corresponding with powered translation of the rackin the forward direction, a first clutch member engaged with the rackthrough at least one intermediate gear, a second clutch member thatreceives torque from the input ring and that is movable in response torotation of the motor in the first direction toward a first positionengaging the first clutch member, and movable in response to rotation ofthe motor in an opposite, second direction toward a second positiondisengaged from the first clutch member, a drive shaft having anon-circular cross-sectional shape with at least one flat, and a hubcoupled for co-rotation with the input ring and having a lug engageablewith the flat in response to rotation of the motor in the firstdirection to transfer torque to the drive shaft, wherein the lug isdisengageable from the flat in response to rotation of the motor in thesecond direction, without rotating the drive shaft.
 2. The powereddispensing tool of claim 1, wherein torque from the motor is transferredto the first clutch member via the input ring and the second clutchmember when the second clutch member is in the first position.
 3. Thepowered dispensing tool of claim 2, wherein the first clutch member isdisengaged from the motor when the second clutch member is in the secondposition.
 4. The powered dispensing tool of claim 3, wherein the rack ismanually translatable in the forward direction and the reverse directionwhen the second clutch member is in the second position.
 5. The powereddispensing tool of claim 1, further comprising: a trigger selectivelydepressed by a user of the tool to activate the motor for rotation inthe first direction, and a control circuit electrically connected withthe motor and operable to rotate the motor in the second direction inresponse to the user releasing the trigger.
 6. The powered dispensingtool of claim 5, wherein the control circuit is configured to rotate themotor in the second direction for a length of time sufficient to permitthe second clutch member to move from the first position to the secondposition.
 7. The powered dispensing tool of claim 5, wherein the inputring is rotated by the motor in an opposite direction when the motor isrotated in the second direction.
 8. The powered dispensing tool of claim1, wherein the transmission further includes a return spring positionedbetween the first clutch member and the second clutch member tofacilitate disengagement of the first and second clutch members inresponse to rotation of the motor in the second direction.
 9. Thepowered dispensing tool of claim 8, wherein the transmission furtherincludes a slide member positioned between the input ring and the secondclutch member, and movable away from the input ring in response torotation of the motor in the first direction, and a delay springpositioned between the slide member and the second clutch member, thedelay spring being compressible between the slide member and the secondclutch member in response to the slide member moving away from the inputring, prior to engagement of the first and second clutch members. 10.The powered dispensing tool of claim 9, wherein the delay spring isconfigured to at least partially expand in response to engagement of thefirst and second clutch members.
 11. The powered dispensing tool ofclaim 9, wherein the input ring includes a first ramp and the slidemember includes a second ramp, wherein the first and second ramps areengageable in response to rotation of the input ring by the motorrotating in the first direction to move the slide member away from theinput ring.
 12. The powered dispensing tool of claim 11, wherein theslide member is movable away from the input ring along a central axiswhich coincides with a rotational axis of the input ring.
 13. Thepowered dispensing tool of claim 11, wherein the first and second rampsare disengageable in response to rotation of the input ring by the motorrotating in the second direction to permit the return spring todisengage the first and second clutch members.
 14. The powereddispensing tool of claim 1, further comprising: a magnet attached to therack, a Hall-effect sensor supported by the housing, and a strokecontrol circuit electrically connected to the Hall-effect sensor and themotor, wherein the stroke control circuit is operable to deactivate themotor in response to the Hall-effect sensor detecting the magnet toarrest powered translation of the rack in the forward direction.
 15. Thepowered dispensing tool of claim 1, further comprising a currentmonitoring circuit electrically connected to the motor and operable todeactivate the motor in response to the electrical current drawn by themotor exceeding a predetermined current threshold for a predeterminedperiod of time.
 16. The powered dispensing tool of claim 1, furthercomprising a motor control circuit electrically connected to the motorand operable to accelerate the motor to an operating speed in responseto initial activation of the motor.
 17. The powered dispensing tool ofclaim 1, further comprising a case at least partially enclosing thetransmission, wherein the case is at least partially enclosed by thehousing.
 18. The powered dispensing tool of claim 1, further comprising:a plunger coupled to one end of the rack, and a cartridge housingcoupled to the housing and defining a longitudinal axis, wherein theplunger is movable within the cartridge housing along the longitudinalaxis in response to powered translation in the forward direction, and inresponse to manual translation in the forward and reverse direction.